1. Field of the Invention
The present invention relates to an audio processing apparatus that plays back multichannel audio data.
2. Description of the Related Art
An audio playback system including a BD (Blue-ray disc) player, an AV amplifier, and a display device is used. Audio data transmitted from the BD player to the AV amplifier is generated by encoding multichannel audio data. For example, as illustrated in FIG. 4, the multichannel audio data includes a left audio signal L, a right audio signal R, a central audio signal C, a low-frequency audio signal SW, a surround left audio signal SL, and a surround right audio signal SR. Recently HD (High Definition)-related audio formats, such as Dolby True HD, Dolby Digital Plus, and DTS-HD, which are used in a BD player, appear on the scene. A surround back left audio signal SBL, a surround back right audio signal SBR, a left outside audio signal LW, a right outside audio signal RW, a left upside audio signal LH, and a right upside audio signal RH are further added in the HD-related audio formats.
However, when amplifiers corresponding to the audio signals of all the channels are provided in the AV amplifier, it is necessary to provide the amplifiers for the total of 11.1 channels, which results in a problem in that a cost increases significantly. The same holds true for the case that, as illustrated in FIG. 7, a left-central-side audio signal LC and a right-central-side audio signal RC are added instead of any one of the extended channels (or in addition to the extended channels). The same also holds true for the case that the AV amplifier generates the extended channels in a DSP according to a listening mode.
An audio processing apparatus in FIG. 15 is conceivable for the purpose of solving the problem. According to the audio processing apparatus, in the case that the surround back left audio signal SBL and the left upside audio signal LH are included, switches S511c and S511e are controlled in an on state, switches S511d, S511f, and S511g are controlled in an off state, the surround back left audio signal SBL is supplied from the DSP to an amplifier 512b through the switch S511c, and the left upside audio signal LH is supplied from the DSP to an amplifier 512c through the switch S511e. Switches S513b and S513e are controlled in the on state, and switches S513c and S513d are controlled in the off state. Therefore, the surround back left audio signal SBL amplified by the amplifier 512b is supplied to a surround back left SP terminal 514b, and the left upside audio signal LH amplified by the amplifier 512c is supplied to a left upside SP terminal 514d (see Japanese Unexamined Patent Publication Nos. 2011-229113 and 2010-183203).
In the case that the surround back left audio signal SBL and the left outside audio signal LW are included, the surround back left audio signal SBL is supplied from the DSP to the amplifier 512b through the switch S511c, and the left outside audio signal LW is supplied from the DSP to the amplifier 512c through the switch S511e. The switches S513b and S513d are controlled in the on state, and switches S513c and S513e are controlled in the off state. Therefore, the surround back left audio signal SBL amplified by the amplifier 512b is supplied to the surround back left SP terminal 514b, and the left outside audio signal LW amplified by the amplifier 512c is supplied to a left outside SP terminal 514c. 
In the case that the left outside audio signal LW and the left upside audio signal LH are included, the left outside audio signal LW is supplied from the DSP to the amplifier 512b through the switch S511c, and the left upside audio signal LH is supplied from the DSP to the amplifier 512c through the switch S511e. The switches S513c and S513e are controlled in the on state, and the switches S513b and S513d are controlled in the off state. Therefore, the left outside audio signal LW amplified by the amplifier 512b is supplied to the left outside SP terminal 514c, and the left upside audio signal LH amplified by the amplifier 512c is supplied to the left upside SP terminal 514d. 
The audio processing apparatus can output the audio signal to a speaker disposed in other pieces of room, such as ZONE2, ZONE3, and ZONE4. A speaker terminal for a ZONE2 left audio signal is also used as the left outside SP terminal 514c. In the case that the ZONE2 audio signal is output, the switch S511d is controlled in the on state, the switch S511c is controlled in the off state, and a ZONE2 left audio signal Z2L is supplied from the DSP to the amplifier 512b through the switch S511d. The switches S513b and S513d are controlled in the off state, and the switch S513c is controlled in the on state. Therefore, the ZONE2 left audio signal Z2L amplified by the amplifier 512b is supplied to the ZONE2 left SP terminal 514c through the switch S513c. Alternatively, in the case that the ZONE2 audio signal is output, the switch S511f is controlled in the on state, the switches S511e and S511g are controlled in the off state, and the ZONE2 left audio signal Z2L is supplied from the DSP to the amplifier 512c through the switch S511f. The switch S513d is controlled in the on state, and the switches S513c and S513e are controlled in the off state. Therefore, the ZONE2 left audio signal Z2L amplified by the amplifier 512c is supplied to the ZONE2 left SP terminal 514c through the switch S513d. 
A speaker terminal for a ZONE3 left audio signal is also used as the left upside SP terminal 514d. In the case that the ZONE3 audio signal is output, the switch S511g is controlled in the on state, the switches S511e and S511f are controlled in the off state, and a ZONE3 left audio signal Z3L is supplied from the DSP to the amplifier 512c through the switch S511g. The switch S513e is controlled in the on state, and the switch S513d is controlled in the off state. Therefore, the ZONE3 left audio signal Z3L amplified by the amplifier 512c is supplied to the ZONE3 left SP terminal 514d through the switch S513e. 
A speaker terminal for a ZONE4 left audio signal is also used as a surround left SP terminal 514a. In the case that the ZONE4 audio signal is output, a switch S511b is controlled in the on state, a switch S511a is controlled in the off state, and a ZONE4 left audio signal Z4L is supplied from the DSP to an amplifier 512a through the switch S511b. The ZONE4 left audio signal Z4L amplified by the amplifier 512a is supplied to the ZONE4 left SP terminal 514a through a switch S513a by controlling the switch S513a in the on state.
At this point, because the speaker terminal for the ZONE4 left audio signal is also used as the surround left SP terminal 514a, it is necessary to connect a ZONE4 left speaker to the ZONE4 left SP terminal 514a in the case that the ZONE4 audio signal is output. In this case, a surround left speaker cannot be connected to the speaker terminal 514a. Accordingly, in the case that the surround left audio signal SL is played back without playing back the ZONE4 audio signal, it is necessary to release the connection of the ZONE4 speaker to the speaker terminal 514a and to separately connect the surround left speaker, which results in a troublesome procedure. Because the surround left audio signal is frequently used, it is necessary to frequently reconnect the speaker in the case that the ZONE4 is used. The reason the speaker terminal for the ZONE4 left audio signal is also used as the surround left SP terminal 514a is that the ZONE2 audio signal, the ZONE3 audio signal, and the ZONE4 audio signal can simultaneously be played back.
FIG. 16 illustrates another audio processing apparatus. In the case that the surround back left audio signal SBL is included, a switch S611c is controlled in the on state, a switch S611d is controlled in the off state, and the surround back left audio signal SBL is supplied from the DSP to an amplifier 612b through the switch S611c. A switch S613c is controlled in the on state, and switches S613d and S613e are controlled in the off state. Therefore, the surround back left audio signal SBL amplified by the amplifier 612b is supplied to a surround back left SP terminal 614b (see Japanese Unexamined Patent Publication No. 2010-183203).
In the case that the left outside audio signal LW is included, the switch S611c is controlled in the on state, the switch S611d is controlled in the off state, and the left outside audio signal LW is supplied from the DSP to the amplifier 612b through the switch S611c. The switch S613d is controlled in the on state, and the switches S613c and S613e are controlled in the off state. Therefore, the left outside audio signal LW amplified by the amplifier 612b is supplied to a left outside SP terminal 614c. 
In the case that the left upside audio signal LH is included, the switch S611c is controlled in the on state, and the switch S611d is controlled in the off state, and the left upside audio signal LH is supplied from the DSP to the amplifier 612b through the switch S611c. The switch S613e is controlled in the on state, and the switches S613c and S613d are controlled in the off state. Therefore, the left upside audio signal LH amplified by the amplifier 612b is supplied to a left upside SP terminal 614d. 
The speaker terminal for the ZONE2 left audio signal is also used as the left outside SP terminal 614c. In the case that the ZONE2 audio signal is output, the switch S611d is controlled in the on state, the switch S611c is controlled in the off state, and the ZONE2 left audio signal Z2L is supplied from the DSP to the amplifier 612b through the switch S611d. The switch S613d is controlled in the on state, and the switches S613c and S613e are controlled in the off state. Therefore, the ZONE2 left audio signal Z2L amplified by the amplifier 612b is supplied to the ZONE2 left SP terminal 614c through the switch S613d. 
The speaker terminal for the ZONE3 left audio signal is also used as the surround left SP terminal 614a. In the case that the ZONE3 audio signal is output, a switch S611b is controlled in the on state, a switch S611a is controlled in the off state, and a ZONE3 left audio signal Z3L is supplied from the DSP to an amplifier 612a through the switch S611b. A switch S613a is controlled in the on state. Therefore, the ZONE3 left audio signal Z3L amplified by the amplifier 612a is supplied to a ZONE3 left SP terminal 614a through the switch S613a. 
At this point, because the speaker terminal for the ZONE3 left audio signal is also used as the surround left SP terminal 614a, it is necessary to connect a ZONE3 left speaker to the ZONE3 left SP terminal 614a in the case that the ZONE3 audio signal is output. In this case, the surround left speaker cannot be connected to the speaker terminal 614a. Accordingly, in the case that the surround left audio signal SL is played back without playing back the ZONE3 audio signal, it is necessary to release the connection of the ZONE3 speaker to the speaker terminal 614a and to separately connect the surround left speaker, which results in a troublesome procedure. Because the surround left audio signal is frequently used, it is necessary to frequently reconnect the speaker in the case that the ZONE3 is used. The reason the speaker terminal for the ZONE3 left audio signal is also used as the surround left SP terminal 614a is that the ZONE2 audio signal and the ZONE3 audio signal can simultaneously be played back.